1. Field of the Invention
The invention relates to gas filters and more particularly relates to reverse gas-flow bag filters for removing solids entrained in a gas, of the type adapted to be mounted in the aperture of a dividing plate so that a gas on one side of the dividing plate is caused to flow into the bag and out at the other side of the dividing plate.
2. Brief Description of the Prior Art
Reverse gas-flow bag filters are described in British Pat. No. 887,772 (published Jan. 24, 1962) together with a complete disclosure of their installation and use in a bag filter housing. In general, this type of bag filter has the structure illustrated in the accompanying drawing of FIG. 1. As shown in FIG. 1, the reverse gas-flow filter comprises a tube 3 fabricated from a filter fabric and having a closed end 4 and an open end 5. The tube 3 is supported by a tubular frame 6 comprising vertical struts 7 tied together and inserted into tube 3 through the open end 5. The tube 3 with its supporting frame 6, is mounted in an aperture of a dividing plate 8 which is a component of a conventional bag filter housing, sometimes commonly referred to as a "bag house". The space between the tube 3 and dividing plate 8 is filled with a gasket material 9 to form an air-tight seal between tube 3 and dividing plate 8. The mounting of tube 3 and the support frame 6 is generally effected by threading the collar of frame 6 and securing it with a large nut (not shown) to the dividing plate 8. In operation, a gas contaminated with solids is directed into the bag house, housing generally a plurality of filter bags mounted on the dividing plate. The contaminated gas passes through the filter, whereupon the solids are left on the outside surface of the bag filter. The filtered gas passes from the filter through the open end 5 for release on the outside of the dividing plate 8. After a period of time, solids build up on the outside of tube 3 and reduce the flow of gas therethrough. To correct this, periodically the flow of gas is reversed to flex the tube walls and cause the built up solids (commonly referred to as a "dust cake") to fall off the filter.
The prior art reverse gas-flow filter bags known heretofore have not been entirely satisfactory for a number of reasons. For example, the requirement for a support frame to support the tubular wall of the fabric bag is costly in terms of the added cost in their initial provision and in terms of their increasing the wear and tear on the fabric bag. More specifically, continued and periodic flexing of the tube or bag wall during reverse gas-flow cycles abrades the fabric where it contacts the supporting frame. This abrasion problem is of such magnitude that heretofore it has been impractical to use the highly abrasion prone glass fabrics for fabrication of reverse gas-flow bag filters. Of course the use of glass fabric bags would be highly desirable and advantageous where the gas to be filtered is maintained at a high temperature, restricting the use of other filter fabrics.
The prior art filter bags have also required relatively costly and complex hardware arrangements for securing to the dividing plate of the bag house. A gas-tight seal with the plate is required. This generally requires separate sealing components and fasteners. In addition, those skilled in the art readily appreciate the manpower requirements for installing, removing and replacing the prior art bag filters with their associated mounting hardware.
The improved reverse gas-flow filter bags of my invention are simple to construct, unitary, do not require a separate support frame upon which the inner surface of the bag can abrade, are quickly installed or removed without special tools and are self-sealing with the dividing plate of the bag housing.
British Pat. No. 1,206,544 discloses a reverse gas-flow bag filter supported by external "stiffening rings".